Obesity is a serious epidemic in our modern society leading to the development of multiple detrimental pathologies. Obesity related disorders can lead to multiple long-term complications such as type II diabetes, cardiovascular diseases, several types of cancer and many other maladies. It is clear that behavioral modifications in diet and energy expenditure can result in weight loss or be the cause of obesity when energy intake exceeds energy expenditure. Much focus has been given to potential pharmaceutical treatment against obesity, especially new approaches are based on the search of functional compounds able to inhibit the digestion of dietary lipids (Shi Y, Burn P; 2004; Lipid metabolic enzymes: emerging drug targets for the treatment of obesity; Nat. Rev. Drug Discover. 3: 695-710).
In the last decades, a great number of enzymes involved in lipid metabolism have been purified and characterized. Lipases that digest fats, both triacylglycerol and phospholipids, are of major interest for obesity. One of the most important lipases is pancreatic lipase (PL) accounting for the hydrolysis of 50-70% of dietary fats (Mukherjee M; 2003; Human digestive and metabolic lipases: a brief review; J. Mol. Catal. Enzym. B 22: 369-376). In the search for antiobesity compounds, PL inhibition has been one of the most widely studied target mechanisms (Birari R B, Bhutani K K; 2007; Pancreatic lipase inhibitors from natural sources: unexplored potential; Drug Discover. Today 12: 879-889). To date, Orlistat, is the only drug accepted in Europe that reduces fat absorption by a peripheral mechanism of action (Lunder M, Bratkovic, T, Kreft, S and Strukelj, B; 2005; Peptide inhibitor of pancreatic lipase selected by phage display using different elution strategies; Journal of Lipid Research 46: 1512-1516).
Additionally, there are considerable evidences from cell and animal studies suggesting the importance of pancreatic phospholipase A2 (PLA2) in the digestion and absorption of lipids. The phospholipase A2 (PLA2) family catalyzes the hydrolysis of membrane phospholipids, releasing arachidonic acid (AA), docosahexaenoic acid (DHA), and other polyunsaturated fatty acids (PUFAs). The released PUFAs are precursors of a variety of eicosanoids, 20 carbon compounds that include prostaglandins, thromboxanes, leukotrienes, and lipoxins responsable of inflammatory reactions. It has been demonstrated that PLA2 and its downstream products can act as important biological mediators in adipose tissue, activation of PLA2 by several cytokines suggests that this enzyme function as cellular links between inflammatory pathways and lipid metabolism thereby constituting a key target in obesity (Abbott M, Tang T mad Sul H; 2010; The role of phospholipase A2-derived mediators in obesity; Drug Discovery Today: Disease Mechanisms 7:3-4).
On the other hand, most of the genes encoding enzymes of lipid metabolism have been cloned and sequenced from different organisms, including humans. Phylogenetic studies have revealed that lipid metabolism is a very well conserved pathway from yeast to humans opening the way to the use of model organisms in the study of antiobesity drugs. In this sense, the nematode Caenorhabditis elegans is a perfect model organism for the study of obesity (Chiang S H, MacDougald O A; 2003; Will fatty worms help cure human obesity; Trends Genet. 19: 523-525). In fact, analysis in C. elegans of fat reducing gene inactivation using interference RNA have identify 305 genes related with reduced body fat and 112 genes involved in increased fat storage, many of them with mammalian homologues (Ashrafi K et al.; 2003; Genome-wide RNAi analysis of Caenorhabditis elegans fat regulatory genes; Nature 421: 268-272). Also in C. elegans, lipases are key factors in obesity. Recent reports of groups working on lipases of C. elegans indicate that in this organism fat metabolism is an unexpected link between obesity, reproduction and aging (Wang M C et al.; 2008; Fat metabolism links germline stem cells and longevity in C. elegans; Science 232: 957-960; Xie T; 2008; Burn fat, live longer; Science 232: 865-866).
Natural compounds potentially preventing the development of obesity and related metabolic disorders have been studied. Gargouri and coworkers reported that some soybean proteins have an inhibitory effect on pancreatic lipase (Gragouri et al; 1984; Studies on the inhibition of pancreatic and microbial lipases by soybean proteins; J Lipid Res., 25:1214-1221). These molecules do not have a direct effect in the enzyme; they modify the lipid emulsions, avoiding the contact between the enzyme and the substrate. In the same way, several authors have explained the presence of basic proteins in some seed with inhibitory properties of lipase activity and later Miyazaki et al., in the U.S. Pat. No. 5,411,956 described some proteins used as inhibitors of lipase in the treatment of obesity (Wang and Huang; 1984; Inhibitors of lipase activities in soybean and other oil seeds; Plant Physiol., 76:929-934; Tani et al; 1994; Purification and characterization of proteinous inhibitor of lipase from wheat flour; J Agri Food Chem., 42:2382-2385; Tsujita et al; 1996; Studies of the inhibition of pancreatic and carboxylester lipases by protamine; J Lipid Res., 37:1481-1487; Gragouri et al; 1984; Inhibition of pancreatic and microbial lipases by proteins; Biochim. Biophys. Acta., 795:326-331).
In the same manner, these and other authors proved that the intestinal lipid absorption was reduced by phenolic substances (i.e., chlorogenic acid, (+) catechin, epicatechin, phloridzin, rutin and procyanidins (condensed tannins)) causing an in vitro inhibitory effect on digestive lipases (Wang et al; 2006; Green tea catechins inhibit pancreatic phospholipase A2 and intestinal absorption of lipids in ovariectomized rats; J Nutr Bioch., 17:492-498), Juhel et al (Juhel et al; 2000; Green tea extract (AR25) inhibits lipolysis of triglycerides in gastric and duodenal medium in vitro; J Nutr. Biochem., 11:45-51), Sugiyama et al (Sugiyama et al; 2007; Oligomeric Procyanidins in Apple Polyphenol Are Main Active Components for Inhibition of Pancreatic Lipase and Triglyceride Absorption; J Agric Food Chem., 55:4604-4609) and Rahul et al (Rahul et al; 2007; Pancreatic lipase inhibitors from natural sources: unexplored potential “Drug Discovery” today., 12:19-20).
However, the study of functional peptides related with obesity, obtained chemically, biotechnologically or by means of enzymatic treatment from proteins, remains an area to explore, although is raising increasing interest. The present invention is focused on functional peptides useful in the treatment of obesity and oxidative stress obtained from microbial digestion of glycinin by using lactic acid bacteria strains.